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y, y. c-'�sz._ lam- .rte.-�10 11 01-A x IF ` ! -t�,, p }} ] "`f v 4 aasiii FINAL REMEDIA71ON PIAN Shell Oil Company g 620 West Charter Way,Stockton,CalifornLi P-_;:xt No.40-88.556 P�gc 17 was designed using a maximum flaw rate of 3 gpm from each pumping well for a total m.admum flow of approximately 15 gpm t If additional off-site wells become necessary,the manifold system may be extended t from either monitoring well MW-7 or MW-9 with minfrnal impact to existing station operations." i 3.7 Interim Free Product SklmmInE and Recovery On December 12, 1989,the hydrogeologic investigation revealed approximately 4.5 feet of free product in monitoring well MW-2" Weekly bailing of frc.c product from monitoring well MW-2 did not reduce the z product thickness,indicating that an automatic product skimming system was warranted. Therefore,anair- nperatc'd biaddr:pump coupled to a floating produ.t shimmer was installed,on,April„13,1940,in monitoring' well-MW-2 Air is supplied to the skimming pump through the compressed air manifold system,and the free product is routes:to storage drums at the remedial equipment area through the water manifold piping system, Apprcmmai,ly 184 gallows of product have be"en'iernoved to dale. The product storage drums are « und:dai�,by a double containment system, and are equipped with a tank-full shutoff to shut off the air compressor to the pump when the drum is nearing capacity. To provide electric power for the air compressor and also!or future remedial equipment installation,a 200-amp temporary electrical service was installed. For a more complete description of the free product recovery system,please see Delta's Interim Remedial Action Plan and Propa;ed Project Schedule letter,dated April 13,1990,presented in Appendix A. 4.0 RF,MF, UL ALTERNATIVr.5 SCREENING AND SELECTION All practical remedial technologies were initially screened for this site. Prior to station reconstruction,the former four underground gasoline storage tanks and product lines were removed,and soil in the immediate vicinity of the tanks were excavated. Approximately 1,140 cubic rrds of soil containing petroleum constituents were Excavated and disposed. Shell then received regulatory approval to proceed,and complete station reconstruction with the condition that any remaining petroleum constituents in the soil and ground water would be cleaned up by in-situ methods. For this reason, Delta installed (in conjunction with the station reconstruction) the manifold system described in Section 3.6 of this report. The,in-situ reme&l technologies,that will,be proposed for the cleanup of the remaining petroleum , constituentslck�tr� nd kround water at the site'wiu be a combination of soil venting and ground.water f recoverg� ,.... ... R��